A head wearable display is a display device worn on or about the head of a user. head wearable displays usually incorporate some sort of near-to-eye optical system to display an image within a few centimeters of the human eye. Single eye displays are referred to as monocular head wearable displays while dual eye displays are referred to as binocular head wearable displays. Some head wearable displays display only a computer generated image (CGI), while other types of head wearable displays are capable of superimposing CGI over a real-world view. The former type of head wearable display is often referred to as virtual reality (VR) while latter type of head wearable display is often referred to as augmented reality (AR) because the viewer's image of the world is augmented with an overlaying CGI, also referred to as a heads-up display (HUD).
Head wearable displays may utilize eye sensing modules to capture image data of an eye of a user. This image data may be used to detect user eye movements, gaze directions, or eye gestures (such as an eye blink or wink). For a head wearable display designed to be worn by a variety of users, these eye sensing modules must accommodate a variety of user eye sizes and locations (i.e., eye regions).